I. Field of the Invention
The present invention relates generally to a method and apparatus of recycling and reusing an aqueous degreasing solution for further use as a component of a cooling solution which is itself recycled and reused in metal cutting machines.
II. Description of the Prior Art
The metal working industry is one of the most heavily regulated industries. One area of this industry that is being scrutinized is the degreasing operation. That is, the metal parts coming out of the cutting machines are covered in metal working fluids and residual lubricants. This occurs because oils are used as lubricants as the raw material is cut to form the finished part. Traditionally, heavy, non-soluble oils were used as lubricants. Vapor phase degreasing was the method of choice for the removal of non-soluble oils from the finished parts. Popular vapor phase degreasers are halogenated solvents as Freon 113; 1,1,1-trichloroethane, trichloroethene, methylene chloride, and tetrachloroethene. These first two are suspected ozone depleters, and the remaining three are suspected carcinogens.
With the introduction of lighter, soluble oils as lubricants in the metal cutting industry, the use of aqueous phase degreasers became a possibility. However, because of the fear of corrosion and also the expense of converting from a vapor to an aqueous phase degreasing process, vapor phase degreasing remained the method of choice.
With the advent of new and more stringent environmental regulations, vapor phase degreasing is becoming a disfavored method of cleaning metal parts. This is so because two of the more common vapor phase degreasers are Freon 113 and 1,1,1-trichloroethane, substances suspected to deplete the earth""s ozone layer. In 1990, Congress passed more stringent laws providing that all parts manufactured by a process involving an ozone depleting substance must be labeled to that effect. This has caused many companies to look to aqueous phase degreasing.
Despite its environmental advantages over vapor phase degreasing with respect to ozone depletion, if not managed properly, aqueous phase degreasing can create environmental problems of its own. The problem of waste water and water pollution is of tremendous concern. As a result, it would be highly desirable for the metal working industry to utilize an aqueous phase degreasing procedure in which the aqueous degreasing solution could be recycled and reused as feeder solution for a metal cutting machine coolant, which is itself recyclable and reusable. Tremendous benefits could be reaped by minimizing worker exposure to harmful substances, as well as reducing or eliminating hazardous waste streams.
A method and apparatus for cooling and washing metal parts which includes washing the metal parts in a degreasing solution, mixing the used degreasing solution with a coolant solution and using the mixture as a coolant in a metal forming operation is disclosed. In this way the wash solution is recycled and reused. The apparatus includes a wash station, rinse station and drying station through which the parts are moved sequentially. The apparatus further includes a counterflow of fluid beginning in the rinse tank and moving downstream through the wash tank at a predetermined rate. The used wash solution is collected for recycling. Also disclosed is a skimming operation and a method of separating degreasing solution from the coolant mixture for recycling in the degreasing system. The method includes using ultrafiltration and precipitation to separate the components.